1. Field of the Invention
The present invention relates to a plasma display panel (PDP), and more particularly, to a PDP having a structure in which each discharge cell is independently defined by barrier ribs formed between two substrates.
2. Description of the Related Art
A PDP is a display device that displays images through the excitation of phosphors. Vacuum ultraviolet (VUV) rays emitted through plasma discharge are used to excite the phosphors. The PDP is experiencing ever-increasing widespread use because of its thin profile and ability to be made with large screen sizes.
FIG. 7 shows a partial exploded perspective view of a conventional PDP. The conventional PDP includes a rear substrate 100 and a front substrate 110 provided opposing one another with a predetermined gap (i.e., discharge gap) therebetween. A plurality of address electrodes 101 are formed on a surface of the rear substrate 100 opposing the front substrate 110. The address electrodes 101 are formed in a stripe pattern along one direction, i.e., substantially along direction X of FIG. 7. A first dielectric layer 103 is formed on the rear substrate 100 covering the address electrodes 101, and a plurality of barrier ribs 105 are formed on the dielectric layer 103. The barrier ribs 105 are formed in a stripe pattern along direction X and at areas between the address electrodes 101. A red, green, or blue phosphor layer 107 is formed between each adjacent (or corresponding) pair of the barrier ribs 105. The phosphor layers 107 cover the dielectric layers 103 between the corresponding pairs of the barrier ribs 105, as well as side walls of the barrier ribs 105.
Formed on a surface of the front substrate 110 opposing the rear substrate 100 are a plurality of display electrodes 114. The display electrodes 114 are formed substantially along direction Y, that is, along a direction substantially perpendicular to the address electrodes 101. Further, each of the display electrodes 114 includes a pair of transparent electrodes 112 and a pair of bus electrodes 113, each of the bus electrodes 113 being formed on a corresponding one of the transparent electrodes 112. A second dielectric layer 116 and a Magnesium Oxide (MgO) protection layer 118 are formed on the front substrate 110 covering the display electrodes 114. Areas between the address electrodes 101 and the display electrodes 114 and delimited by the intersection of these elements form discharge cells.
With the above configuration, if an address voltage (Va) is applied between the address electrodes 101 and the display electrodes 114 to produce an address discharge, then a sustain voltage (Vs) is applied between a pair of the display electrodes 114 to produce a sustain discharge. The VUV rays generated during the sustain discharge then excite the corresponding phosphor layer 107 so that it emits visible light. The visible light passes through the front substrate 110 to thereby realize the display of images.
However, a problem with forming the display electrodes 114 in the stripe pattern and the barrier ribs 105 in the stripe pattern as described above is that crosstalk may occur between adjacent discharge cells, that is, between the discharge cells adjacent along direction Y. Further, since the discharge cells are communicating between each adjacent pair of the barrier ribs 105 (i.e., along direction X), there is the possibility of mis-discharge occurring between the adjacent discharge cells in this direction. To prevent this latter problem, the spacing between the display electrodes 114 along direction X is increased. However, this runs counter to efforts for improving PDP efficiency.
U.S. Pat. No. 5,640,068 discloses an attempt to overcome these drawbacks. Although stripe-type barrier ribs are used in the PDP disclosed in this patent, the transparent electrodes forming the display electrodes are structured to include a base portion extending horizontally and a projecting portion extending perpendicularly from the base portion so that a pair of the projecting portions is formed opposing one another at every pixel region. However, mis-discharge problems along the direction that the barrier ribs are formed still remain with this structure.
Another common configuration found in PDPs is to form the barrier ribs in a matrix structure, in which the barrier ribs are formed to perpendicularly intersect one another. Such a formation is used to overcome the drawbacks as discussed above and also to increase the area of deposition of the phosphor material in an effort to enhance illumination efficiency. The invention disclosed in Japanese Laid-Open Patent No. Heisei 10-149771 utilizes such a configuration. However, in the matrix type of barrier rib structure, since all areas except those directly corresponding to where the barrier ribs are formed are areas where discharge takes place, there are no regions in the PDP that absorb or disperse heat, only areas that generate heat. As a result, temperature differences result between discharge cells where discharge takes place and where discharge is not occurring. Such temperature differences not only adversely affect discharge characteristics, but are also the cause of other problems such as brightness differences and bright image sticking. (Bright image sticking refers to the phenomenon in which an illuminated region maintains its brightness level for a period relative to surrounding regions even after the illuminated region has been controlled to return to the pattern of its surrounding regions.)
Another prior art drawback relates to the manufacture of the PDP. The barrier ribs of the PDP are formed to a desired pattern using a barrier rib material through either a screen-printing process, or a conventional sandblasting process in which predetermined areas of a barrier rib material are removed following uniform deposition of the same. Drying and firing are also performed as part of patterning process of the barrier ribs. However, a problem with forming barrier ribs using these methods is that during the firing process, organic material contained in the barrier rib material is removed such that the barrier ribs shrink and are otherwise deformed.
Such deformation of the barrier ribs is particularly severe at end areas of the barrier ribs in non-display regions of the PDP. This is a result of a shrinking force being concentrated at the ends of the barrier ribs. An example of such deformation of barrier ribs is shown in FIG. 8, in which an end area of one of the barrier ribs 105 of FIG. 7 is shown prior to and following the firing process. As shown in FIG. 8, the end of the barrier rib 105 curls away from the rear substrate 100 to be separate therefrom. One negative consequence of such deformation of the barrier ribs is that the noise generated by the PDP may become severe.